java 时间的操作

java代码：

//由今天的时间获取昨天的时间

public static String getSpecifiedDayBefore(String specifiedDay) {
Calendar c = Calendar.getInstance();
Date date = null;
try {
date = new SimpleDateFormat("yyyyMMdd").parse(specifiedDay);
} catch (ParseException e) {
e.printStackTrace();
}
c.setTime(date);
int day = c.get(Calendar.DATE);
c.set(Calendar.DATE, day - 1);

String dayBefore = new SimpleDateFormat("yyyyMMdd").format(c.getTime());
return dayBefore;
}